Electric filtration system



May 10, 1938. F. G. coTTRELL ELECTRIC FILTRATION SYSTEM Filed oct. 2. 195s 2 Sheets-Smet 1 f/v ds/v Toe.- Feeose/ag Gmane@ Carreaux YWfl 14 frog/v5.1

May 10, 1938. F. G. coTTRELL ELECTRIC FILTRATION SYSTEM Filed Oct.' 2, 1953 2 Sheets-Sheet 2 Patented May 10, i938 i SVY PATENT OFFICE ELECTRIC FILTRATION SYSTEM Frederick Gardner Cottrell, washington, D. c.,

asdgnor to Petroleum California, Los Angeles,

California Rectifying Company of Calif., a corporation of 'Application october 2, 193s, serial No. 691,806

22 Claims.

This invention relates to Aa method and apparatus for removing foreign material from a liquid by the use of an electric field which is preferably of a unidirectional character. More particularly, the invention 'comprehends the application of cataphoretic principles in a novel manner.

.'I'heproblem of separating foreign material from a liquid phase has been long recognized. Attempts have been made to move such foreign material from the liquid by applicationl of a unidirectional elect'ric field so that the foreign particles migrate toward one or the other of the electrodes where they are deposited. However, it is seldom possible to remove al1 traces of this foreign material. For this'reason l. have found it desirable to utilize aiilter material in conjunction with an electric field, and such a system is included among the objects of the present invention.

Another feature of the invention is to maintain 2o at least a portion of the foreign material is moved away from this surface through cataphoretic Vaction, thus preventing accumulation' of a large quantity of the foreign material on `the filter itself. In this way it is possible to' eliminate much of the frequent cleaning of a filter surface such as is necessary in existing processes wherein filtration alone is utilized for separating the foreign material.

Another feature of the present invention is to move the mixture through a distributing member, and to set up an electric field into .which the mixture moves, this field acting to stop or com- `pletely reverse the direction of movement of the foreign material in the mixture. be so designed as to return this foreign material to the distributing member from which it came.

Another feature of the present invention resides in the use of a movable member on which the a foreign material is deposited so that this member can be removed from the fluid either continuously or intermittently so that a cleaning thereof can be effected and so as to present new surfaces to the fluid.

It should not be understood, however, that it is in all instances necessary to utilize an electric field of sufficient intensity to cause foreign material to deposit on one or the other of the electrodes. The invention also comprehends a process wherein the electric field maintains theforeign material suspended therein while the liquid phase can now therethrough, this forel-gn material remaining in the field and increasing the concentration therein until such time as it bean electric field adjacent a filter surface so that The field can l comes desirable to remove this concentrated material therefrom.

By proper design of the system it becomes possible to maintain in the electric field foreign particles which are both positively and negatively charged, as will be hereinafter set forth, and one of the features of the present invention is to subject the incoming mixture to such a field whereby the oppositely charged particles not only tend to themselves neutralize and thus form` .larger masses, but-also tend to contact the dispersed particles of the incoming mixture to unlte'therewith in forming masses of larger size.

One process with which the present invention finds particular utility is the electrical dehydration of petroleum emulsions. Such a conventional dehydrating process includes the building up of an velect-ric field, usually of alternating character and of hi-gh intensity, so as to coalesce dispersed water droplets of the petroleum emulsioninto masses of sufficient size to gravitate from the oil. The meeting of present commercial standards requires that such a dehydration system reduce the water content of the oil to at least 3%. In many instances, however, it is desirable to remove even a. greater proportion of the water, and it is in this capacity that the present invention can be utilized, the emulsion being first subjected to an alternating current field and later subjected to a unidirectional field after a certain amount of settling has taken place.

The above and still `further features and objects of the invention will be evident to those skilled in the art from the following description.

Referring to the drawings:

Fig. ll diagrammatically illustrates the simple form of treater capable of carrying out the process.

Fig. 2 illustrates the treating system in conjunction with an electric dehydrator.

Fig. 3 is an alternative form of combined treater and dehydrator.

Figs. 4 and 5 are alternative forms of the treater shownin Fig. l.

Referring particularly to Fig. 1, I have diagrammatically shown a tank I0 across which al porous member Il extends to define-an intake chamber I2 to which the incoming mixture is supplied through a pipe i3. This porous member is preferably one having relatively good electrical insulating properties `and is relatively coarsegrained toprovide interstices which are of greater size than the dispersed particles of the incoming mixture. This mixture may thus move through the porous member H and into a treatof the foreign material on the intake surface of this porous member. So also. the'foreignV-material is in the form of a dispersed liquid, the

' prevent any further subdivision 0f these drop.

provision of-intersticesin the porous-member II of larger size than the dispersed droplets will lets as the mixture moves through this member.

` An electric iield is set up in the treating space I5 by any suitable means. In the form shown the porous member` Il supports an"interstitial electrode vI5 which extendsonly partially across this memberso that theend portions of this porous member act to insulatethe'electrode from the tank. It ispossible to form this elect-rodeby various means. Thus, the porous surface of Y the member IIl can 'be sprayedvor. otherwise the interstices of this porous'member.

coated with a metallic substance to form the interstitial electrode'V I6, care being. exercised not to deposit suiiicient conducting material to'close In other instancesit is possible to mount a metallic screen or perforated plate along this. surface of the. po-

rous member II, as diagrammatically shown in Fig.. 1. In any event -aconductor I`I supplies a potential to this electrode 'I6 and extends through a suitable bushing I B and to one terminal of a lgenerator I9 preferably off the direct-current A iilter plate 22 extends across the tank- VII! .and separates the treating space I5-from a discharge chamber '2 3 communicating with a pipe 24. This lter plate is'pre'ferably formed of a i "filter material'having only very minute pores.

Usually it is desirable'to utilize a filter plate -which would in itself iiiter from the mixture some or all of the foreign material of the mixture. The material Aforming this iilter plate may vbe one having Agood electrical insulating properties so as to' itself act as an insulated support for an interstitial` electrode 25 extending therealong but spaced from th'etank III. This interstitial electrode may be formed in a manner similar to the electrode liso that the liquid of the Amixture -can readily pass therethrough. A oo nductor 21 energiz this electrode; and extends vthrough a bushing 28 andis also connected to the generator I9. "I'his generatorv may be of the.

variable-voltage type whereby the potential between the electrodes I 6 and 25 may be varied.

Ifdesired, a variable. resistance.l may be yinf serted in series with this generator to4 control this j potential.

In the' operatic-rn of this form voi' vthe invention -the mixture to be treated enters the intake chamber I2 through the pipe I3, and the porous mexn-v ber I I acts as a distributing means for discharging this mixture into thetreating space I5. In the .absence of any electric field in thistreating space, thismixture will move rightwardther'eacross-lat -a uniform velocity and the foreign an electric ileld is impressed between' the electrodes I5 and 25'. "the.action onthe foreign `par ticles will depend-upon the inherent charge thereon. a The neld canv vbe ,built up so as to either increase or retard the normal movement of these foreign particles as they are carried along with the liquid'. Usually I iind it preferable to utilize an electric iieldwhich acts not only to retard `the forward Amovement of theseioreign'parti-j cles toward the iilter plate 22, but actually to f 2,11e,5o9' v Vstances return the foreign particlestowardA the become quickly clogged by such a deposit. The

pores of -the member II `are relatively large and v are not'easly. Vclosedby a deposit of the foreignv material, even if this foreign material is in the form of a solid substance. If the foreign material isin the form of a liquid, at least a portion of this liquid will come into contact with .the porous member Il or the electrode and may move downward therealong by gravitational force if the liquid thus accumulated is of greater density'than the continuous phase ofthe and will move upward if of less density.Y

Ihe electrodes I6 and 25 do not form iields of uniform gradient thereadjaoent. Instead, the field is concentrated at sections along the metallic members of the screen,or adjacent the crests or minute edges of the electrodes. Thus. while some of the foreign material will' be deposited on the porous member II or the electrode I6, 'other of the foreign particles will be subjected to a somewhat different action as they move leftward against the rlghtward flowing. stream of liquid. When these particles come into thevicinity of one of the high field-intensity portions of the iield adjacent the electrode I5, they appear to come into electrical contact therewith, thereby' receiving the charge of the electrode, and are then repelled from the electrode -in the-direction of ilow of the mixture through the treating space I5. Apparently, the ileld conditions adjacent the electrode I5 control thisV action. Thus the system may be so designed and operated that" some ofA the foreign particles reaching the most intense portions of the ileld are subsequently discharged from the vicinity of the electrode I6 rather than clinging thereto, these particles thus discharged of course moving toward the electrode 25 which is of opposite sign. In fact, they move through the treating space I5 at a velocity controlled both by the electric iield and the stream .of mixture, these particles thushaving a net velocity which is higher than the mixture. Some of these particles may come into contact with the electrode 25 and be thereon deposited. Other of these particles will be repelled from the electrode 25 after they have come into electrical contact therewith and have thus received a chargewhich is opposite in sign to the charge which they possess when moving rlghtward. The net eil'ect is that the treating space I5 contains particles of foreign material some of which are charged' positively and some of which are charged negatively.. There is a force tending to bring such oppositely charged particles into contactwith each other if they are suiciently close. 'ihe result is o f course that such particles join together and the charges thereon are substantially neutralized. 'If the particles comprise liquid droplets they coalesce and thus tend to ldrop in the treating space Il. being possibly contacted during their downward movement by other charged particles of the 15 foreign material moving between the electrodes. 8o also, the charged particles thus moving in the iield tend to come into contact with the. particles of foreign material newly introduced into the field, thus tending to facilitate separation thereof.

n the other hand, the field will contain charged particles which move therein without becoming neutralized and which particles will travel back and forth in the field. This is shown by the fact that the material in the treating space Il increases in concentration as treatment Thus, in some instances substantially all of the foreign material is vdeposited on the electrodes. but in other instances a portion of this foreign material remains suspended in the treating spa so that eventually 'it is desirable to remove the concentrated material therefrom. This may be done intermittently. the material being moved through a pipe 3| communicating :witha funnel I2 of the tank Il. In other instances it is possible to continuously remove a small portion of the liquid in the treating space Il through the pipe ll.

Referring to Fig. 2 Iv have illustrated a treating apparatus similar to that shown in Fig. 1 as used in conjunction with an electric dehydrator 3l. This dehydrator may be of conventional construction including a tank 36 in which live and grounded electrodes Il and 3l are respectively positioned to define a treating space 39. 'I'he incoming emulsion is delivered through a pipe Il to a pump Il which forces it into the treating space I! where it is subjected to an electric eld set up by a `transformer I2 connected to supply lines as shown. 'I'his eld acts to coalesce the dispersed water particles of the incoming emulsion, and the coalesced masses settle in the tank I and are withdrawn through a pipe M. The 011 rises in the tank 3i and is withdrawn through a pipe l5. 'Ihis oil is not, however, usually in a pure state, but carries a small percentage oi' water therewith.

A treater similar to that shown in Fig. 1 is illustrated as being connected to the pipe 45 so that this mixture oi' oil and water ilows thereoi' this treater preferably communicates with the intake oi' the pump Il and includes a valve 46 controlling the flow therethrough. The pump Il 0 thin can be used to draw the Awater or other mixture from the treater and return this to the electric held of the dehydrator for further treatment or disposal. The dry oil moves through the pipe 2l of the treater to a suitable storage means. In this form of the invention I have illustrated a motor-generator set I1 connected to the supply lines I3 and supplying the potential to the electrodes Il and 25.

In the form of the invention shown in Fig. 3, both treaters are enclosed in a single tank 5D. Here the incoming emulsion moves through a pipe Il and through a nozzle'52 surrounding a rod electrode 5I maintained at ground potential. A live electrode in the form of a shield 54 is positioned therearound, cooperating therewith in delining a treating space 55 in which coalescence takes place. 'lhe heavier constituent ofthe emullion moved from the tank 50 through a pipe Il. while the substantially dry oil moves upward 0 into a chamber 5I defined between a dome 59 and a porous member lll. This material then mom through the porous member and into a heating space Il wherein a unidirectional ileld h prderably established. In this form an inter- 5 stitial electrode I2. corresponding to the electrode arranca through as previously described. The pipe 3| Y 3 I5 previously described, is shown as being placed immediately inside the porous member Il. A central electrode il of relatively small sine extends therein. Any suitable means may be utilized for setting upa unidirectionalileldinthespacebetween electrodes l2 and 53. In the form shown I have illustrated a transformer Il as su alternating current to the electrodes 5I andjl. and a vaculnntube or other reciifying device 'Il connected to the incoming line and delivering unidirectional current vto the electrodes 52 and 53. If desired a suitable choke and filter system may be used in conjunction with the rectifying device 'il so as to eliminate some or all of the ripples which would otherwise appear in the potential delivered to these electrodes.

In this form of the invention the oil,v together with a minute amount of water carried therewith, moves through the porous member andthrough the electrode i2 and into the electric ileld. This eld is preferably designed to move the dispemed particles of water toward the electrode fl so that this water can coalesce around this electrode and drop from the lower end thereof and into a funnel 12 which discharges above a distributor plate 13 thus preventing direct return of this water to the treating space 55 but delivering same to the ileld around the electrode 54. In other instances, however, it is possible to reverse the connections on the electrode so that the water particles willbe moiled toward the outer electrode 52, flowing therealong and into the funnel 12. In any event the dry oil is removed through a pipe 14 and delivered to a suitable storage.

This form of the invention utilizes a ileld which is more intense adjacent the central electrode Il than adjacent the electrode 62, this eld being thus of non-uniform intensity. Such an electrode structure is often advantageous when certain types of mixtures are being treated, regardless of whether these mixtures comprise water particles or solids suspended in an`oil phase.

In Fig. 4 I have illustrated a Systemfwherein at least a portion of the, foreign material is deposited on a moving member and then withdrawn from the treating space. A tank Il is illustrated, one portion of the tank'comprising an intake chamber 8| bounded by a porous member I2 and a wall 83. The mixture may be delivered to this intake chamber through al pipel Il. and flow through the porous member and into a treating space l5. An electrode II similar to that previously described is mounted on the porous member 82. Similarly, a discharge chamber l1 is formed in. the opposite end of the tank Il being bounded by a lter plate 8l and a wall Il. This filter plate preferably mounts an electrode Il similar to the electrode previously described.

A roller 9| is shown as being rotatably' mounted below the filter plate 8l and a corresponding roller 92 is positioned thereabove and outside -the tank 80. A movable member, preferably in the form of a continuous belt 53, extends ltherearound. One of the rollers is suitably driven so that the belt 93 moves upward adjacent the electrode Il. This belt means is preferably interstitial in character and may be formed of metallic screen as shown. In other instances this belt may' be of cloth, preferablyA formed of a material which is water wettable It is not, however. necessary that this belt be formed of conducting material in all instances, though if ever it is thus formed it will be clear that the belt can be in actual electrical contact with the electrode il, if desired. The beit would uien :n itself comprise an rs vil electrode. In other instances' the belt can .be spaced slightly therefrom as shown. In any event any electricl field is established in the treatingv -of a sol-id material, as, for instance, carbon, this material will be deposited en the external sur-l face of the belt and can be removed therefrom by suitable means spaced above the tank 80 and shown as comprising a scraper 91 dischargingv into a hopper 98. The liquid phase of the mix' ture moves through the filter -plate 88 andv into; the discharge chamber 81 whence it is Withdrawn j through a pipe 99.

In the form of the invention shown in Fig. 4

the downward moving portion of the belt 93 isV shown as moving. through the chamber 81. l'If this is undesirable a form such as `shown in. Fig. 5 may be utilized. Here the discharge chamberv is indicated by the numeral' lill and is` formedf by e an open-ended shell |02 closed. by a filter plate |03 similar to that previously described.' j A` discharge pipe |04 conducts the liquidtherefrom.

This shell is positioned directly above the -lower roller 9| and between the upward andjdownward- `moving portions of the belt 93. The entire tank 80 may be filled with liquid'to a level indicated by the numeral Ilil.l Alsoin this form of the'` invention a scraper |01 may beused for remov ing any Imaterial carried-upward by the belt 93,

. this material sliding down a plate |08 and into a VhopperlliS. Y

It is sometimes possible to reverse the direction of flow through the forms shown in Figs. 4 and 5, discharging the pure liquid through the pipe 8l and, if desired, reversing the position of the porous member and lter plate. Usually,

VVhowever, this is not preferable in view of the fact that the incoming mixture must iiow through the belt means before moving into the central portion of the field. However, with a belt of interstitial character, this system can often be used and the -belt `can thus act as a porous member through which the incoming mixture moves. With such a -ow it is usually desirable to maintain the unidirectional field of such character as Yto return the foreign material to the belt 93 from which it is removed at a position outside the tankll.

In other instances a belt means may be provided adjacent the porous member 82 as Well as the' filter plate 88, thus removing from the vicinity of the electrode 86 any foreign matter which mightfotherwise deposit on this electrode' due to the action of the, electric iield.

I claim as my invention:

1. A method'oi' treating a mixture of a liquid and a suspended material, which method includes the steps of forming a stream of said mixture moving in a given direction; setting up an electric field acting to move said suspended material in a direction opposite to said given direction and at a velocity greater than the velocity of said stream oi.' said mixture; and collecting said suspended material.

y2. A method of treating a mixture of a liquid and a. suspended material, which method includes the steps of forming a. stream ol' said mixture moving in a given direction; setting up an electric eld acting to move said suspended material -in a direction opposite to said givendirection whereby the concentration of said suspended maf.` terial in said iield increases as treatment pro-l gresses, the lines of forcein said field being sub- I stantially parallel to the direction of flow; ,and

removing lsaidsuspended mattery from 'saldi-field;

3; A method. of ltreatingv amixturebf aY liquid and a suspended materialfby the use ofl a'filter plate having interstic'es of smaller size than the particles oisaidsusp'ended: matter and by the use of a porousmember having interstices of larger size than said particles`which method includes the steps iik-'continuously moving a stream oi said mixture'throug-h said porous member and f toward said iiltergplate; establishing an electric field of unidirectional characterfin the-space be-1' vtween lsaid porous member and lsaid filter'plate and oi'a character to ca'taphoreti'cally move said particles in a direction toward said porous member therebyfpreventing deposit oi said particles I on. said lter plate; .and vmoving said liquid through said filter plate fto remove any particles not removed -by `said electricfield. f fi. A methodk of treating a mixture of a liquid and a suspended material by 'the use of a porous member havingjinterstices of larger size than said suspended material, which method includes the steps of: flowing 'said' mixture continuously through saidporous. member; 'and establishing an Aelectric field through which said mixture movesvafter passing through said porous member, said electric field acting to cataphoretically move the particles of ksaid suspended rmaterial in a *direction toward' said porous member andlinto contact therewith.v v -1 y 5. A method as'deiined in claim 4 in which said porous :member forms one electrode for establishing said electric field thus bounding said i'leld.

6. A method of electrically treating a mixture to separate the constituents thereof, which method includes the steps of establishing an alternating and a unidirectional electric eld; moving said mixture into the alternating-held; partially separating said constituents; moving. one of the constituents thus partially separated into said unidirectional field wherein vtheremainlng constituents are separated; and returning by'gravity' one of said constituentsthus separz'atedl in said unidirectional iield .to said alternating ileld.

7. In combination inanelectriclseparating device for treating a mixtureoi aliquid and a suspended material: a v'illter plate; Y disposed adjacent a iorwarcfisurf ter plate; a second electrode-disposed in spaced relationship with `said first electrode and positioned on the same side oi' said illterfplate as said iirst electrode; means for movingthe `suspended particles in a direction awayirom said 'filter plate and including' means for establishing a' po-, tential dliferencebetween saidelectrodes with the potential so maintained that the electricileld thus established betweensaid electrodes acts to move theV suspended'particles to be; separated away from said iilter plate; means for continu.

' ously flowing said mixture in said field toward said' filter plate; and means for withdrawing said liquid after it has passed through said illter plate; i 8. In combination in an electric separating dei vice for treating a mixture of a" liquid and a suspended material: a filter plate providing an interstitial surface of electrical conducting-material and forming a first electrode; a second elec# trode disposed in spaced relationship with said iilter plate; means for setting up an electric iield between said first and said second electrodes and acting to move the suspended particles to be sepplate.

9. In combination in an electric separating device for treating a mixture of a liquid and a suspended material: a porous member; a filter plate spaced from said porous member to define a space therebetween; means for flowing said mixture through said porous member and toward said llter plate: and means for establishing a unidirectional electric ileld in said space to attract said suspended material and prevent deposition of the whole of said suspended material on said filter plate, said liquid moving through said filter plate.

' 10. In combination in a treater for separating a mixture of a liquid and a suspended material: a tank containing said mixture; a movable interstltial member of lelectric conducting material and forming a first electrode, the surface of said interstitial member being movable from submerged position in said mixture to a position above said mixture; means for moving said interstitial member to move said surface from said submerged position to said position above said mixture; a second electrode in front of said first electrode; means for establishing an electric field between said electrodes tending to move said 'suspended material toward said first electrode of interstitial character; 'a filter means to the rear of said first electrode and receiving the liquid and any unseparated suspended matter passing through said interstitial member; and means for withdrawing said liquidpassing through said filter.

1 1. In combination in a treater for separating a mixture of a liquid and a suspended material: a tank containing said mixture; a movable interstitiar member and providing a front portion and another portion spaced therefrom, both portions being in said tank; a filter means between said portions of said movable interstitial member and receiving any liquid and unseparated suspended material moving through said front portion of said movablejinterstitlal'member; means for moving said liquid toward said front portion' of said movable interstitial member and thence through said filter means and said other portion in succession; and means for withdrawing the puried liquid which passes through said filter means and said other portion of said movablefintcrstitial member.

'12. In combination in an electrical treating system for mixtures: means setting up an electric field of alternating character; means for circulating the mixture to be treated in said field; means for establishing an electric field of unidirectional character above said field of alternating character and into which moves at least a part of said mixture for separation of the suspended material therein, said unidirectional and said alternating fields being in open communication whereby the suspended material in said unidirectional fleld drops to said field of alternatingcharacter.

13. In combination in an electric dehydrator: a tank containing a dry-oil zone in the upper end thereof. the emulsion to be treated being in a lower emulsion zone of said tank; an interstitial cylindrical electrode in said dry-oil zone and bounding an electric field; means for moving material inward through the interstices of said cylindrical electrode, at least a portion of said material moving downward from the interiore! said cylindrical electrode; and means for establlshing an electric field of alternating character in said emulsion zone and to which field said portion of said material reaching the interior of said cylindrical electrode is delivered.

14. A method of treating an emulsion by the use of a cylindrical interstitial electrode, which method includes the steps of: setting up an electric field adjacent said cylindrical electrode moving a treated portion of said emulsion into the interior of said cylindrical electrode through' the interstices thereof establishing an electriceld of alternating character below said interstitial electrode; moving at least part of the treated portion of said emulsionentering said interstitial electrode downward from the interior thereof and into said field of alternating character; andl introducing additional emulsion to be treated into said eld of alternating character.

15. A method of separating the phases of an emulsion' by the use of a belt-like interstitial member, which method `includes the steps of: first passing said emulsion through one portion of said interstitial member whereby some of the particles of said emulsion are deposited thereon and removed from the emulsion; then moving the remaining emulsion through a illter with small pores to remove additional emulsion particles; moving said interstitial member to present fresh surfaces to said emulsion; and moving the liquid through another portion of said interstitial member after it moves through said filter means.

16. In combination in an electric separating device: a vstationary filter means; an interstitial electrically-conducting member in the form of a continuous belt-like member having one side in front of said stationary filter means. said stationary filter means being positioned between opposite sides of said interstitial member; means for movably mounting said interstitial member; means flowing a liquid containing suspended particles toward said interstitial member and thus tending to continue on to said lter means; means for electrically depositing a portion of said particles on said interstitial member, the remaining liquid moving through said stationary filter means, said means including electrode means cooperating with said interstitial member and establishing an electric ileld in said liquid moving toward said interstitial means; and means for moving said interstitial member to present new deposit-receiving surfaces to said electric field.

17. A method of separating a suspended material from a liquid by use of a filter member providing an interstitial electrically-conducting surface, which method includes the steps of: moving the liquid with its suspended material toward said interstitial electrically-conducting surface; establishing an electric field adjacent said interstitial electrically-conducting surface of sumcient intensity to charge and project at least a portion of the suspended material from said surface in a direction away from this surface; and collecting the liquid after it mov through said filter member. t

18. A method of removing suspended impurities from a. liquid by-the use of a lter and cataphoretic action, which includes the steps of: flowing a stream of said liquid containingsaid suspended impurities toward one side of said filter so that said liquid ows therethrough; setting up a uni-directional field of sufficient intensity and proper polarity immediately adjacent said vimpurities toward one side oi' said filter so that said oil flows therethrough; setting up a unidirectional ileld of suillcient intensity and proper v polarity in said stream flowing toward said filter to cause cataphoretic movement of at least a portion of said suspended impurities in a direction opposite to the direction of movementof said stream and away from said lter.

20. A method as defined in claim 1 involvingthe use of a iilter plate toward which said liquid ilows and including the step of moving said liquid through such lter plate immediatelyv after subv jection to said electric'fleld and as it continues its movement toward said lter plate whereby said electric field moves said suspended material -in a g5 direction away i'rom said filter plate.

Patent No. 2,116, 509.

CERTIFICATE 0F QORREGTION.

FREDERICK GRDNER'COTTRELL.

21. A combination as deiined in claim 1i in which said filter means is between and spaced from said portions of said movable interstitial member.

22. In combination in a treater for separating suspended material from a liquid: a tank containing a body of said liquid; an interstitial member movable in said body of liquid and providing front and rear portions spaced from each other; a lter between said portions of said movable interstitial member and receiving any liquid and unseparated suspended material moving through said front portion of said movable interstitial member; means for moving the liquid containing suspended material toward said front portion of said movable interstitial member and thence through said iilter means; walls defining a discharge chamber between said portions of said movable interstitial member and receiving the purified liquid issuing from said nlter; and means for`conducting said purified liquid from said discharge chamber.

FREDERICK GARDNER COITREIL.

It is hereby certified that error appears inf-the printed specification of the above numbered patent requir ing correction as follows: Page 5, second column, line 10, claim 1h., after the 4win/fd e1ectrode". insert asemicolon; and that the said Letters Patent/.should be read with this correction therein that the'same' may conform tothe record vof the case in the Patent Office.

Signed and sealed this 28th dayofJune, A. D. 1958.

(Seal) Henry Van Arsdale `Acting Commissioner of- Patents.-

vimpurities toward one side oi' said filter so that said oil flows therethrough; setting up a unidirectional ileld of suillcient intensity and proper v polarity in said stream flowing toward said filter to cause cataphoretic movement of at least a portion of said suspended impurities in a direction opposite to the direction of movementof said stream and away from said lter.

20. A method as defined in claim 1 involvingthe use of a iilter plate toward which said liquid ilows and including the step of moving said liquid through such lter plate immediatelyv after subv jection to said electric'fleld and as it continues its movement toward said lter plate whereby said electric field moves said suspended material -in a g5 direction away i'rom said filter plate.

Patent No. 2,116, 509.

CERTIFICATE 0F QORREGTION.

FREDERICK GRDNER'COTTRELL.

21. A combination as deiined in claim 1i in which said filter means is between and spaced from said portions of said movable interstitial member.

22. In combination in a treater for separating suspended material from a liquid: a tank containing a body of said liquid; an interstitial member movable in said body of liquid and providing front and rear portions spaced from each other; a lter between said portions of said movable interstitial member and receiving any liquid and unseparated suspended material moving through said front portion of said movable interstitial member; means for moving the liquid containing suspended material toward said front portion of said movable interstitial member and thence through said iilter means; walls defining a discharge chamber between said portions of said movable interstitial member and receiving the purified liquid issuing from said nlter; and means for`conducting said purified liquid from said discharge chamber.

FREDERICK GARDNER COITREIL.

It is hereby certified that error appears inf-the printed specification of the above numbered patent requir ing correction as follows: Page 5, second column, line 10, claim 1h., after the 4win/fd e1ectrode". insert asemicolon; and that the said Letters Patent/.should be read with this correction therein that the'same' may conform tothe record vof the case in the Patent Office.

Signed and sealed this 28th dayofJune, A. D. 1958.

(Seal) Henry Van Arsdale `Acting Commissioner of- Patents.- 

